The present invention relates to a new and improved construction of an actuating system for a bobbin tube gripping device or bobbin tube gripper.
In its more particular aspects, the present invention specifically relates to a new and improved construction of an actuating system for a bobbin tube gripping device, particularly but not exclusively for securing bobbin tubes relative to a chuck structure in a filament winding machine. Such actuating systems are designed particularly, but not exclusively for use with chuck structures of the type as described in the aforenoted cross-referenced commonly assigned, copending U.S. application Ser. No. 911,816, filed Sept. 26, 1986, entitled "CHUCK STRUCTURES".
In actuating systems for bobbin tube gripping devices such as known, for example, from U.S. Pat. No. 3,052,420, granted Sept. 4, 1962, U.S. Pat. No. 3,554,455, granted Jan. 12, 1971, and 4,068,806, granted Jan. 17, 1978, the bobbin tube gripping device on a chuck in a filament winder contains a wedging "cone" in the shape of a truncated cone which is axially movable in order to urge gripping elements radially outwardly into engagement with the internal surface of a bobbin opposite direction in order to permit the gripping elements to return radially inwardly for releasing the internal surface of the previously gripped bobbin tube. In an alternative system such as known, for example, from U.S. Pat. No. 3,815,836, granted June 11, 1974, and U.S. Pat. No. 4,336,912, granted June 29, 1982, so-called wedging devices of a shape different from the aforementioned wedging cones are employed.
It is also normal practice to urge the wedging devices in the operating or gripping direction by means of a mechanically generated biasing force. Thus, in the absence of a specially applied releasing force, the elements gripping the bobbin tube are normally pressed outward in a gripping direction. Suitable means are of course provided to limit their movement in the outward or gripping direction in the absence of a bobbin tube to be gripped. The release force is normally applied by a pressure-fluid operated device, such as a piston-and-cylinder unit.
The mechanical biasing force is conventionally produced by a spring device and such spring devices have frequently been in the form of so-called "cup-springs" or "Belleville washers". Such spring devices normally comprise a plurality of spring elements, each in the form of a concave/convex disk. The concave/convex disks are arranged neighbor at its outer rim on the concave side and the other neighbor at its inner rim on the convex side. Spring devices increase.
Firstly, there is the problem of unbalance in the chuck structure. Some degree of play is necessary at the assembly stage in order to enable insertion of the spring devices into the remainder of the chuck structure. This leads to problems in centering the spring devices relative to the chuck structure and can lead to shifts of individual elements from the desired positions relative to their neighbors. The resulting slight imbalance is normally acceptable at lower winding speeds such as are encountered at linear thread speeds up to about 4,000 meters per minute, but leads to increasing problems at higher winding speeds.
Secondly, there is the problem of the large number of elements required to provide the relatively high gripping forces which must be produced at higher winding speeds. This problem has a number of aspects. An increasing number of elements takes up additional space within the chuck structure. Furthermore, an increasing number of elements makes it difficult to maintain uniformity of the spring characteristic of the individual elements. As a result, some elements may "collapse" when the spring device is loaded and this produces a non-uniform spring characteristic for the device as a whole. Furthermore, as the number of elements in the spring device rises above 20 to 30, careful checking becomes necessary in order to ensure that the correct number of elements is inserted into each spring device. Finally, the cost of the spring device as a whole becomes significant as the number of elements is substantially increased.